We have developed techniques to specifically radioactively label carbohydrate portions of cell membrane glycoproteins and glycolipids. By applying such methods followed by polyacrylamide gel electrophoresis and autoradiography, we have previously shown that purified populations of normal human blood leukocytes have characteristic and distinguishable surface glycoprotein patterns which clearly correlate with the stage of cellular maturation and activation and that various cultured benign and malignant leukocyte cell lines can be characterized by their surface glycoprotein profiles. We have recently shown that the human leukemia cell line K562 is erythroid and can be induced to red cell differentiation in vitro. In this proposal we intend to: 1) isolate and characterize surface glycoproteins characteristic for subpopulations of normal human blood leukocytes. For these studies we have a massive supply of normal human leukocytes (buffy coats from 70000 blood units a year); 2) by radiolabeling of surface glycoproteins of malignant leukocytes from patients with leukemia or lymphoma further refine methods for accurate classification according to cell type of origin and stage of differentiation and to identify surface proteins associated with certain types of hematopoietic malignancies; 3) characterize the specific changes in the surface glycoprotein expression of the human erythroleukemic cell line K562 during induced erythroid differentiation, and study the biosynthesis of well-defined erythrocyte components; 4) further establish the usefulness of surface glycophorin A as a marker for early erythroid differentiation in acute leukemia.